In many medical procedures, such as drug delivery, it is desirable to inject a fluid into a patient. Likewise, numerous types of contrast media (often referred to simply as contrast) are injected into a patient for many diagnostic and therapeutic imaging procedures. For example, contrast media are used in diagnostic procedures such as X-ray procedures (including, for example, angiography, venography and urography), CT scanning, magnetic resonance imaging (MRI), and ultrasonic imaging. Contrast media are also used during therapeutic procedures, including, for example, angioplasty and other interventional radiological procedures. Regardless of the type of procedure, any fluid injected into the patient must be sterile and contain a minimum of pyrogens.
A number of substantial problems arise in the use of current pumping systems and methods for injecting fluid into a patient's body. For example, it is often difficult to accurately control the pressure and flow rate of the fluid exiting the pumping system. Although peristaltic pumps have long been successfully used in relatively low pressure applications, for example, peristaltic pumps are difficult to control with accuracy.
In the case of relatively high pressure applications, such as CT and angiography, mechanized syringe injectors are used. The use of mechanized syringe injectors also results in a number of substantial drawbacks. Current mechanisms for powering and controlling syringe pumps are complicated, inefficient and costly. Expensive and bulky pressure jackets for housing the syringe pumps are often required to prevent failure at high pressures. Syringe pumps are severely limited in that only the volume of fluid contained in the syringe can be injected at one time. Disposable syringe pumps are costly. Moreover, the rise time of syringe injectors is limited by the inertia of the extensive drive train required to translate motor rotation into syringe plunger motion.
These and other drawbacks in current syringe pumping systems create and magnify a number of inefficiencies in current procedures for injecting contrast media. For example, a number of factors, including, but not limited to, the procedure to be performed and the size of the patient, determine: (i) the contrast to be used, (ii) the concentration thereof, and (iii) the amount to be injected. Under current practice of injecting contrast media via syringe pumping systems, hospitals must purchase and stock many contrast media concentrations in multiple container sizes in an attempt to provide the correct concentration and amount of a specific contrast for a specific procedure, while minimizing the wastage of contrast. In that regard, contrast is typically very expensive.
Thus, most contrast media are provided by manufacturers in numerous concentrations in sterilized containers (such as glass bottles or plastic packages) ranging incrementally in size from 20 ml to 200 ml. These containers are generally designed for a single use (that is, once a container is opened for a patient, it is used for that patient only). The contrast is generally aspirated from such containers via the syringe pump used to inject the contrast, and any contrast remaining in the container is discarded to prevent infection with potentially contaminated contrast. The hospital staff is faced with the task of choosing an appropriately sized contrast container to assure an optimum study while minimizing discarded contrast. Time consuming procedures are required to reload the syringe if more contrast is required than originally calculated. On the other hand, expensive waste results if only a portion of a filled syringe is injected. The inventory of contrast containers required under the current system increases costs and regulatory burdens throughout the contrast media supplier-consumer chain.
Many of these costs, regulatory burdens and other problems associated with the use of multiple contrast containers can be substantially eliminated through use of relatively large contrast media containers for single- and multiple-patient use in connection with a pumping system allowing any volume and concentration of contrast to be injected as determined by the hospital staff before or during a procedure. Current syringe pumping systems simply do not provide a sufficiently cost-effective and efficient pumping system to provide optimal pressurization for injection of contrast and other liquid media.
It is, therefore, very desirable to develop pumping systems that reduce or eliminate the limitations associated with current pumping systems.